Electrically actuated valves are known for a variety of applications, including in the automotive field. For example, in an engine, an electrically actuated valve may be used to control the recirculation of exhaust gases back to the engine cylinders in an exhaust gas recirculation (EGR) system.
An electrically actuated valve comprises a valve element which is movable between a first end in which the valve is fully open and a second end, opposite the first end, in which the valve is fully closed. The position of the valve element between the first end and the second end establishes the extent to which the valve is open. The valve may include a mechanical stop at the first end to prevent the valve element from moving beyond the first end and a mechanical stop at the second end to prevent the valve element from moving beyond the second end.
Applying an electrical signal of a first polarity to the electrically actuated valve may cause the valve element to move in a first direction, i.e. towards the first end, and applying an electrical signal of a second polarity, opposite to the first polarity, to the electrically actuated valve may cause the valve element to move in a second direction opposite to the first direction, i.e. towards the second end.
In certain conditions, valves and their associated control systems may behave unexpectedly. For example, in response to the application of an electrical signal to the electrically actuated valve, the valve element may move generally more slowly than is expected (which might be described as a “sluggish” valve) or it might favour moving from some positions over other positions (which might be described as a “sticky” valve) or it might fail to move altogether (a “stuck” valve). All of these might be described as valve faults.
Against this background there is provided a method and control system for detecting such valve faults and applying a valve control strategy which seeks to remedy such faults.